Photochromic behavior of ZnO/MoO3 interfaces.

Ines Andron (1) , Léa Marichez (1) , Veronique Jubera (1) , Christine Labrugère (1, 2) , Mathieu Duttine (1) , Christine Frayret (3) , Manuel Gaudon (1)

1 ICMCB - Institut de Chimie de la Matière Condensée de Bordeaux
2 PLACAMAT - Plateforme Aquitaine de Caractérisation des Matériaux
3 LRCS - Laboratoire réactivité et chimie des solides - UMR CNRS 7314

ZnO/MoO3 powder mixture exhibits a huge photochromic effect in comparison with the corresponding single oxides. The coloring efficiency of such combined material after UV-light irradiation was studied in terms of intensity, kinetics, and ZnO/MoO3 powder ratio. Additionally, the incidence of the pretreatment step of the ZnO and MoO3 powders under different atmospheres (air, Ar or Ar/H2 flow) was analyzed. The huge photochromic effect discovered herein was interpreted as the creation of “self-closed Schottky barrier” at the solid/solid interfaces between the two oxides, associated with the full redox reaction which can be pictured by the equation ZnO1−ε + MoO3 → ZnO + MoO3−ε. Remarkable optical contrast between virgin and color states as well as self-bleaching in dark allowing the reversibility of the photochromism is emphasized. From this first discovery, deeper characterization of the self-bleaching process shows that the photochromic mechanism is complex with a bleaching efficiency (possibility to come back to the virgin material optical properties without any deterioration) and a bleaching kinetics, which are both dependent on the coloring irradiation time. This demonstrates that the oxygen exchange through the Schottky interface proceeds in at least two convoluted steps: an anionic surface exchange allowing a reversibility of the redox reaction followed by bulk diffusion of the exchanged anions which are then definitively trapped. An emergent “negative photochromism effect” (i.e., photochromism associated with a self-bleaching instead of a darkening under irradiation) is observed after a long irradiation time.

Mots clés: photochromism; Schottky barrier; interfaces; photoredox; zinc oxide; molybdenum oxide

Domaines: Chimie théorique et/ou physique; Chimie inorganique; Matériaux

Ines Andron, Léa Marichez, Veronique Jubera, Christine Labrugère, Mathieu Duttine, et al.. Photochromic behavior of ZnO/MoO3 interfaces.. ACS Applied Materials & Interfaces, 2020, 12 (41), pp.46972-46980. ⟨10.1021/acsami.0c13335⟩. ⟨hal-02982997⟩